1. Field of the Invention
The present invention relates to an endoscopic passage-confluent structure that joins a liquid feed tube and a gas feed tube together into connection to a confluent tube communicating with an ejection nozzle, in a cleaning mechanism arranged in an endoscope and for feeding a cleaning fluid, of a liquid or a gas, to a viewing window arranged at the tip of an insertion portion thereof.
2. Description of the Related Art
The endoscope, particularly for medical use, is provided with a viewing window at the tip of its insertion portion in order to observe the body interior. During endoscopic examination, the viewing window is possibly contaminated with body fluids, etc. For this reason, a cleaning mechanism is provided for the viewing window. The cleaning mechanism is constructed with an ejection nozzle arranged nearby the viewing window, a feed passage of a cleaning fluid, e.g. a cleaning liquid or a pressurized gas, leading to the ejection nozzle, and a control mechanism for control of feeding the cleaning fluid. When the viewing window is contaminated, a cleaning liquid is issued at the ejection nozzle to clean away the contaminants on the viewing window, followed by feeding a pressurized gas to the ejection nozzle. This can remove the droplets adhered to the viewing window. Here, the cleaning water can use water while the pressurized gas can be air. This makes it possible to keep well the field of sight through the viewing window without taking the insertion portion out of the body interior.
The control mechanism can be operated with a finger of the hand gripping the body control portion of the endscope. Specifically, this is formed by water-feed and gas-feed valves, or a gas/water feed valve formed with water-feed and gas-feed valves in one body. For this reason, the feed passage is arranged with the water and gas tubes respectively connected to the water-feed and gas-feed valves. Those tubes are both in communication with the ejection nozzle. Here, because cleaning water and pressurized air are fed in order instead of being ejected at the same time, the ejection nozzle is usually structured for feeding both water and gas, in order to reduce the diameter of the insertion portion. There is an arrangement that the water-feed and gas-feed tubes are joined together at the inside of the body control portion by the request of reducing the diameter of the insertion portion. For example, Japanese Patent No. 3,678,614 discloses a structure that the confluent tube is provided at the tip of the insertion portion by joining the water-feed tube and the gas-feed tube together at the inside of the body control portion.
This Japanese Patent No. 3,678,614 discloses two types of conduit confluent structures. Firstly, there is a branch structure that a bend tube is connected to an intermediate point of one tube provided straight. In this case, any one of the water-feed and gas-feed tubes is connected to the bend tube while the other is to one end of the straight tube wherein the confluent tube is connected to the other end of the straight tube. Meanwhile, the other confluent structure uses a confluent member in a block form. The confluent member is formed with a penetrating flow passage extending straight. Meanwhile, a flow passage, parallel with the penetration flow passage, is formed extending from one end to intermediate point of the confluent member. By opening a flow passage orthogonal to the same, confluence is provided with the penetration flow passage. Consequently, the confluent member has two openings of flow passages at its one end and one opening of flow passage at the other end. Water-feed and gas-feed tubes are respectively connected to the two flow passages at the one end while a confluent tube is connected to the other end.
In using a branch structure or a block-formed confluence member, the confluence structure in Japanese Patent No. 3,678,614 is structurally provided by forming one straight flow passage and joining the other flow passage with the straight flow passage. For this reason, because fluid flow is straight through one of the two conduits connected to the confluence member, the resistance to flow is less thus forming a smooth flow. However, the flow passage joined to the straight flow passage is bent sharply in its route and hence considerably great in the resistance to flow, thus resulting in a conspicuous pressure loss with a turbulent flow at the confluent point. Therefore, a considerable great difference encounters between the fluids flowing through the two flow passages.
In the branch structure, the conduit is weak at the connection because of providing a through hole in the straight conduit and connecting a bend conduit by means of soldering or welding. Here, the branch conduit is provided within the body control portion wherein other members are arranged within the body control portion. For example, there is a possibility that the branch tube is urged by a manipulation-tool receiving channel, various operation wires, etc. Thus, the connection is possibly broken or cracked by the reaction of such an external force. Because of a cleaning liquid used as a cleaning fluid, the liquid if leaks through the broken point would cause a contamination in the interior of the body control portion.
Meanwhile, where using a block-formed confluent member, there is a no fear of breakage or the like. However, because such a block structure requires a greater size as compared to the branch structure, there is a difficulty in obtaining a sufficient space for arrangement in the body control portion. Besides, there is a fear that the block urges the received members, such as light guides and cables, provided in a manner passing through the body control portion, into a disconnection.